The present invention relates to an internal combustion engine having individual hydraulic circuit modules for hydraulically controlling cylinder deactivation in individual cylinders of the engine.
Valve deactivation is used for improving fuel efficiency in engines. Valve deactivation cuts off one-half of the available cylinders by deactivating valve lift in those cylinders so that such cylinders remain closed after a combustion cycle of the engine, and the burnt gases remain trapped within the cylinder during deactivation.
Some valve deactivators are used in internal combustion engines having a push rod type valve gear train in which there is a rocker arm, with one end of the rocker arm engaging a push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head by a fulcrum arrangement in which the fulcrum normally prevents movement of the central portion of the rocker arm in an xe2x80x9cup and downxe2x80x9d direction. At the same time, the fulcrum permits the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical motion of the push rod, which results from the engagement of the push rod with the lobes of the rotating camshaft.
There are a number of known valve deactivator assemblies which are operably associated with the fulcrum portion of the rocker arm and which, in the latched condition, restrain the fulcrum portion of the rocker arm to move in its normal cyclical, pivotal movement. However, in an unlatched condition, the valve deactivator assembly permits the fulcrum portion of the rocker arm to engage in xe2x80x9clost motionxe2x80x9d such that the cyclical, pivotal movement of the push rod causes the rocker arm to undergo cyclical, pivotal movement about the end which is in engagement with the engine poppet valve. In other words, the rocker arm merely pivots, but the engine poppet valve does not move, and therefore is in its deactivated condition.
U.S. Pat. No. 6,196,175 discloses a valve deactivator which is incorporated into a cam follower assembly, and is hydraulically actuated. This device includes an outer body member which engages and follows the cam, and an inner body member disposed within the outer body member and reciprocable relative thereto. The inner body member includes means for transmitting the cyclical motion of the cam to the remainder of the valve gear means when the outer and inner body members are in a latched condition. A latch assembly is positioned within the inner body member when in the unlatched condition, and includes a radially movable latch member. A source of pressurized fluid, such as oil, is operatively associated with the latch assembly, and is operative to bias the latch member toward the unlatched condition.
A hydraulically-actuated valve deactivator, such as that described in the ""175 patent, requires pressurized oil for operation. A hydraulically-controlled cylinder deactivation system typically uses this pressurized oil to control the switching member of the system in a manner to deactivate cylinders through lost motion of the inlet and exhaust valves. A single custom module is generally provided to receive the pressurized oil from an engine and to provide the hydraulic supply, exhaust and control of the oil which is needed to operate the switching member (such as the valve deactivator of the ""175 patent) for all deactivatable cylinders.
In the single custom module, the system of channels used to supply the hydraulic oil to all of the switching members can be complex and difficult to package within an engine. Also, such devices typically include a three-way valve, which may be slow in actuating a valve deactivator.
Accordingly, it is desirable to provide an improved valve deactivation system with reduced complexity and improved speed of operation.
The present invention provides an individual hydraulic circuit module for each engine cylinder having deactivation capability. These single cylinder modules have the advantage of simplifying the hydraulic circuit. They allow any cylinders to be deactivated, and the design allows sharing between different engine families because the individual hydraulic circuit module could be fit onto any engine. These modules also reduce the cost of service because a bad module can simply be removed for repair or replacement.
More specifically, the invention provides an internal combustion engine having hydraulically-controlled cylinder deactivation, including an engine block with an oil supply gallery and a plurality of cylinders formed therein. At least one-half of the cylinders are deactivatable by collapsible lifters. The engine block includes first and second lifter openings adjacent each deactivatable cylinder and includes the collapsible lifters in the lifter openings. First and second deactivator feed channels communicate the first and second lifter openings, respectively, with a top surface of the engine block. A supply channel communicates the top surface with the oil supply gallery. An individual hydraulic circuit module is connected to the top surface adjacent each deactivatable cylinder and includes a hydraulic plate with a flow channel formed therethrough in communication with the respective first and second deactivator feed channels and with the respective supply channel. The individual hydraulic circuit module also includes a solenoid valve for selectively blocking oil flow from the flow channel to an exit port of the module to selectively build oil pressure in the flow channel and in the lifter openings to actuate the collapsible lifters to enable cylinder deactivation.
Another aspect of the invention provides that each solenoid valve is a two-way, on/off valve which is operative to selectively discommunicate the flow channel from an exit port to cause oil pressure to build up in the flow channel to actuate the collapsible lifters.
Preferably, the flow channel in each hydraulic plate is configured to slope upwardly in a direction toward the respective solenoid valve to assist in purging air from the hydraulic circuit module.
Another aspect of the invention provides a solid cover plate covering the respective supply channels and deactivator feed channels adjacent those cylinders which are not deactivatable. Preferably, each hydraulic plate and cover plate is substantially the same size and has similarly situated attachment holes to facilitate interchangeability of hydraulic plates and cover plates.
Preferably, a flow control orifice is positioned between the supply channel and the flow channel to increase fluid flow velocity and reduce parasitic losses. The flow control orifice may be integral with a filter positioned in the supply channel.
Accordingly, an object of the present invention is to provide an improved hydraulically-controlled cylinder deactivation system which employs individual hydraulic cylinder modules for each deactivatable cylinder to provide hydraulic control of cylinder deactivation for such cylinders.